M41x0.75 female to M42x1 male thread adapter, adjustable

This adapter consists of two parts - body with M42x1 male thread and screw-in insert with M41x0.75 female thread.

It is purposed to mount a lens with M41x0.75 male thread onto a focusing helicoid M42x1 thread when flange focal distance (FFD) of the lens is unknown.

Screwing the insert to necessary depht allows tuning of the FFD to reach infinity focus.

You can tight a set screw then to secure found position.

Take note that you should know approximate FFD of your lens to calculate properly which focusing helicoid extension you need.

This adapter adds 25-35mm to the optical path.